Gastrointestinal (GI) bleeding is a large and serious clinical problem. Occult GI bleeding is found in as much as 3-6% of the American population over the age of 50 and can be an important warning sign for colorectal cancer. Therefore, the finding of occult bleeding mandates a rather expensive and uncomfortable medical work-up to determine if the bleeding is from a lower or upper GI source and to rule out the presence of a colorectal cancer. However, most patients with GI bleeding with an upper GI source which does not represent a colorectal cancer. However, most patients with GI bleeding have an upper GI source which does not represent a colorectal cancer. Therefore, the development of an accurate, practical and inexpensive test to differentiate between upper and lower GI bleeds could result in a tremendous savings of health care resources. In addition, such a test would be better accept4d by patients with an increased compliance for diagnosis. It is the aim of this research project to develop a simple, practical and inexpensive test that could characterize a GI bleed as upper or lower and be accomplished at the point of care. PROPOSED COMMERCIAL APPLICATIONS; This product will be a point of care, non-invasive test to help in localizing the site of bleeding in the GI tract. The largest market for this test will be in the evaluation of patients with occult blood in their stool. Colorectal screening programs find about 4-6% of the population over the age of 40 have positive tests which represents a potential market of about 6 million patients (or about $70 million per year)> In addition, this is a demographically expanding market that will help assure commercial success.